A positive displacement pump dispenser is one which is actuated by a hand applied downward force to an upper portion of the dispenser to cause rams located in a bottom portion to contact and move pistons in product containing cylindrical chambers located in the upper portion upwardly to thereby dispense the products in the chambers from the dispenser. This is in contrast to vacuum actuated pump dispensers where pistons in the product containing cylinders move upwardly by means of a vacuum being formed in each chamber during the dispensing operation, the vacuum causing each piston to move upwardly to dispense the products from the dispenser. Positive displacement pump dispensers have been found to be very effective for the delivery of multiple products from multiple chambers. They usually have a lower cost. Fewer parts are required, including valves. Vacuum actuated pump dispensers usually require two valves for each product chamber to create the vacuum in each chamber necessary for dispensing. This increases the number of parts and consequently the cost of the dispenser.
The prior art with regard to positive displacement multichamber pump dispensers is exemplified by U.S. Pat. No. 3,166,221, European Patent 292,672, U.S Pat. No. 5,020,694 and U.S Pat. No. 5,038,963. In U.S Pat. No. 3,166,221 there is an upper product chamber and a lower base having a ram to fit into each upper product chamber. The pistons that slideably fit into the product chambers are an integral part of the rams. The upper product chamber and the lower base do not have any structure to increase the stability of the upper part in the base part nor any structure to decrease the force to actuate the dispenser. Likewise in U.S Pat. No. 5,020,694 the pistons are a part of the rams. Conceptually, this dispenser is similar to that of U.S Pat. No. 3,166,221. In European Patent 294,672 the pistons are not attached to the rams but rather form the bottom closure of the product chambers. In U.S. Pat. No. 5,038,963 there is disclosed a multichamber pump dispenser with improved features over the dispenser of U.S Pat. No. 5,020,694, but there is no structure to increase stability during use nor any means to reduce the force to actuate. Also there is no structure to enhance the structural integrity of the dispenser. Regardless of these deficiencies, these references evidence the present state of the art of multichamber pump dispensers.
One problem faced by those developing multichamber pump dispensers is the uniform dispensing from each chamber. Another problem is to maintain a low force to actuate the pump. The first problem can be solved by maintaining close tolerances between the interfitting sliding pieces. The second problem can be solved by minimizing the contact areas of the interfitting pieces. However, these are contrary solutions. Generally, close tolerances will require more contact of interfitting parts. This will reduce the variance between the parts and thus, the tendency of one part to move irregularly into the other, but it will increase friction and the force to actuate. The solution to one problem will have a negative effect of the other problem. Uniquely, the present invention solves both problems. There is a more uniform dispensing and a decrease in the force to actuate.
Another problem that is solved is a positive locking system of the upper portion of the dispenser and the base portion. This is accomplished by a mechanism that extends from a lower part of an upper shroud to at least one of the rams of the base portion. This provides for a concealed, positive locking mechanism to lock the upper shroud in an extended position. It also will prevent the upper shroud from being fully disengaged from the base portion during use or during the replacement of the product chambers with refill unit product chambers.
Another problem that is solved is to increase the rigidity of the dispenser parts. This is accomplished for an upper shroud by having an inwardly projecting ledge at the base of the upper shroud. In a preferred embodiment this ledge forms a floor at the base of the upper shroud. For the base lower shroud this is an inwardly projecting ledge at the upper edge of the base lower shroud which substantially rigidifies the base shroud.
A further problem that is solved is the reduction in the drag of the products from each chamber in passage through spout conduits to the spout exit. This is accomplished by the diameter of each conduit being greater in cross-sectional area adjacent the product chambers and at the spout exit. Intermediate the product chambers and the spout exit, the channels decrease in cross-sectional area and then increase in cross-sectional area to the spout exit. The cross-sectional area increases by means of the walls opposite the spout divider wall diverging outwardly. This shape of these conduits produces a decreased drag of the products by the conduit walls.
The present dispenser design solves these and other problems. The unique design provides a multichamber pump dispenser that uniformly dispenses the products from each chamber at a low force to actuate. There also is a unique locking mechanism of the upper portion and the lower portion and an increase in the rigidity of the primary dispenser parts. Additionally there is less drag in the dispenser spout which further reduces the force to actuate. These are useful commercial advantages of this dispenser.